It is conventional practice in connection with the manufacture of printed wiring boards to adhere an electrically-conductive metal lamina upon a thin, glass fabric-reinforced, polymerized resin substrate, to then selectively coat desired electric current pathways on the adhered metal lamina with a photo-sensitive etchant resist, and to afterwards remove unprotected portions of the metal lamina from adhesion to the substrate component by etching whereby only electrical current pathway metal remains adhered to the reinforced and polymerized resin substrate. Subsequently, mounting holes for the leads of various to-be-added electrical circuit elements are drilled through the retained pathway metal and supporting substrate, the electrical leads of various added electrical elements are inserted in the mounting holes, and the inserted electrical leads are afterwards soldered to the pathway metal by dipping of pathway metal and inserted leads into a pool of molten solder. Another conventional method used for creating metal pathways is to selectively plate conductive materials directly onto the reinforced and polymerized resin substrate.
Also, the known printed wiring boards have hereto been manufactured using conventional resins such as known epoxy, bismaleimide, or cyanate resin systems for the assembly glass fabric-reinforced substrate component. The use of such resin systems in the substrate component have consequently and undesirably required the use of solders that have lower melting temperatures and lower operating environment temperatures than those of the comparatively high-temperature solders that may be advantageously utilized in the practice of our invention. Further, the conventional or prior art printed wiring boards have necessarily utilized a less-dense spacing of inserted electrical component leads than can be advantageously obtained by practice of our invention.
The above-mentioned advantages of the present invention are attributed primarily to the nature of the resin system we utilize in the manufacture of the printed wiring boards, to particular resin system and reinforcement processing to form the printed wiring board substrate component B-staged preform, or completely cured preform, and to the improved adhesion of electrical current pathway metal, usually copper, to the substrate component B-staged preform that is obtained in the course of subsequent metal cladding lamination or alternatively adding metal to the completely cured preform by chemical, plasma, or ion vapor deposition. Still other advantages of the present invention will become apparent during consideration of the various descriptions which follow.